Body Mass Impacts Metabolic Rate

Higher lean body mass necessitates more energy to sustain metabolism, resulting in a higher resting metabolic rate. Conversely, lower body mass leads to reduced resting energy expenditure. This relationship is critical for understanding metabolic adaptation, where a disproportionate reduction in metabolic rate occurs relative to body mass lost. The total daily energy expenditure comprises three components: resting metabolic rate, diet-induced energy expenditure (thermic effect of food), and activity-related energy expenditure. The thermic effect of food accounts for the energy used in digestion, absorption, transport, and storage of nutrients, typically causing a 10-15% increase in energy expenditure for the first few hours after a meal. Higher calorie, protein, or fiber intake enhances the thermic effect, raising energy demands for processing food.